All books, records, and payrolls of the employers showing or reflecting in any way
upon the amount of wage expenditures of such employers shall always be open for inspection
by the assistantsecretary or any other authorized auditor, accountant, or inspector for the
purpose of ascertaining the correctness of the wage expenditure and number of men
employed and such other information as may be necessary for the purposes and uses of the
assistant secretary in the administration of the Workers' Compensation Act. No person shall
be excused from testifying or from producing any book, record, or payroll in any
investigation or inquiry, by or upon any hearing before the workers' compensation judge,
when ordered to do so by the workers' compensation judge, upon the ground that the
testimony, payroll, or other competent evidence required of him may tend to incriminate him
or subject him to penalty or forfeiture; but no person shall be prosecuted, punished, or
subjected to any penalty or forfeiture for or on account of any act, transaction, matter, or
thing concerning which he shall have under oath, by order of the workers' compensation
judge, testified to or produced documentary evidence of, provided however, that no person
so testifying shall be exempt from prosecution or punishment for any perjury committed by
him in his testimony.